Fluid ejection apparatus

ABSTRACT

A fluid ejection apparatus is disclosed. One apparatus includes a first head chip and a second head chip. The first head chip includes nozzle groups A1, A2, B1 and C. The second head chip includes nozzle groups D2, E1, E2 and F. The nozzle groups A1, A2, B1, C, D2, E1, E2 and F eject fluid at an average usage rates A1, A2, B1, C, D2, E1, E2 and F, respectively. The average usage rate A2 is smaller than the average usage rate A1. The average usage rate B1 is smaller than the average usage rate A1. The average usage rate C is smaller than the average usage rate A1. The average usage rate D2 is smaller than the average usage rate E2. The average usage rate E1 is smaller than the average usage rate E2. The average usage rate F is smaller than the average usage rate E2.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No.2016-071043 filed on Mar. 31, 2016, the content of which is incorporatedherein by reference in its entirety.

FIELD OF DISCLOSURE

The disclosure relates to a fluid ejection apparatus.

BACKGROUND

A known fluid ejection apparatus, e.g., an inkjet recording apparatus,includes a recording head. The recording head includes two head chips,each having a plurality of nozzle rows or arrays. Each nozzle row ejectsa corresponding one of different color inks. The two head chips arearranged in a predetermined direction such that an overlap head zone(e.g., transition zone) is defined. The inkjet recording apparatuscontrollably ejects respective color inks from each of the head chips tothe overlap head zone, to prevent print density unevenness fromoccurring at a portion of a recording sheet corresponding to the overlaphead zone. The portion of a recording sheet corresponding to the overlaphead zone may be referred to as the “portion A” of the recording sheetand other portion of the recording sheet corresponding to other zone ofthe recording head than the overlap head zone may be referred to as a“portion B” of the recording sheet. The inkjet recording apparatus usesnozzles of each nozzle row of the two head chips at predeterminedrespective usage rates across an entire portion of the overlap headzone.

SUMMARY

The inkjet recording apparatus switches the use of nozzles of eachnozzle row of one head chip to nozzles of a corresponding nozzle row ofanother head chip in the entire portion of the overlap head zone. Suchnozzle switching performed for all colors in the same portion of theoverlap head zone may cause differing ink deposition orders between theportion A of the sheet and the other portion B of the sheet. Thediffering ink deposition orders may cause different hues between theportions A and B of the sheet, resulting in a deterioration ordegradation of an image quality.

In one configuration, nozzles of each nozzle row of one head chip may beswitched to nozzles of a corresponding nozzle row of another head chipat a respective one of different positions. This configuration mayincrease the overlap head zone defined by the two head chips. This maylead to increase in the number of head chips required for the recordinghead.

One or more aspects of the disclosure provide a fluid ejection apparatusthat may reduce a width of a transition or an overlap head zone betweentwo head chips while reducing a deterioration of quality of an imagerecorded on a recording medium. Another aspect of the disclosureprovides a control method of the fluid ejection apparatus.

According to one aspect of the disclosure, a fluid ejection apparatusincludes a first head chip extending from a first end in a firstdirection towards a second end in the first direction. The first headchip includes a nozzle row A comprising nozzles A arranged along thefirst direction, a nozzle row B comprising nozzles B arranged along thefirst direction and a nozzle row C comprising nozzles C arranged alongthe first direction. The fluid ejection apparatus includes a second headchip extending from a third end in the first direction towards a fourthend in the first direction. The second head chip includes a nozzle row Dcomprising a plurality of nozzles D arranged along the first direction,a nozzle row E comprising nozzles E arranged along the first direction,and a nozzle row F comprising nozzles F arranged along the firstdirection. The fluid ejection apparatus includes a controller configuredto control the first head chip and the second head chip to eject fluidfrom the first head chip and the second head chip. The nozzle row B ispositioned between the nozzle row A and the nozzle row D in a seconddirection orthogonal to the first direction. The nozzle row D ispositioned between the nozzle row B and the nozzle row E in the seconddirection. The nozzles A of the nozzle row A are arranged into a nozzlegroup A1 and a nozzle group A2. The nozzle group A1 comprises some ofthe nozzles A. The nozzle group A2 comprises others of the nozzles A.The nozzle group A1 is positioned between the nozzle group A2 and thecenter of the first head chip in the first direction. The nozzles B ofthe nozzle row B are arranged into a nozzle group B1. The nozzle groupB1 comprises some of the nozzles B. The nozzle group A1 and the nozzlegroup B1 are aligned along the second direction. The nozzles C of thenozzle row C are arranged into a nozzle group C. The nozzle group Ccomprises some of the nozzles C. The nozzle group A1 and a portion ofthe nozzle group C are aligned along the second direction. The nozzles Dof the nozzle row D are arranged into a nozzle group D2. The nozzlegroup D2 of the nozzle row D comprises some of the nozzles D. The nozzlegroup A2 and the nozzle group D2 are aligned along the second direction.The nozzles E of the nozzle row E are arranged into a nozzle group E1and a nozzle group E2. The nozzle group E1 comprises some of the nozzlesE. The nozzle group E2 comprises others of the nozzles E. The nozzlegroup A1 and the nozzle group E1 are aligned along the second direction.The nozzle group A2 and the nozzle group E2 are aligned along the seconddirection. The nozzles F of the nozzle row F are arranged into a nozzlegroup F. The nozzle group F comprises some of the nozzles F. The nozzlegroup A1 and a portion of the nozzle group F are aligned along thesecond direction. The nozzle group C and the nozzle group F are alignedalong the second direction. The controller is configured to control thenozzle group A1 to eject fluid at an average usage rate A1 that is anaverage of usage rates of the some of nozzles A comprising the nozzlegroup A1. The controller is configured to control the nozzle group A2 toeject fluid at an average usage rate A2 that is an average of usagerates of the others of nozzles A comprising the nozzle group A2. Thecontroller is configured to control the nozzle group B1 to eject fluidat an average usage rate B1 that is an average of usage rates of thesome of nozzles B comprising the nozzle group B1. The controller isconfigured to control the nozzle group C to eject fluid at an averageusage rate C that is an average of usage rates of the some of nozzles Ccomprising the nozzle group C. The controller is configured to controlthe nozzle group D2 to eject fluid at an average usage rate D2 that isan average of usage rates of the some of nozzles D comprising the nozzlegroup D2. The controller is configured to control the nozzle group E1 toeject fluid at an average usage rate E1 that is an average of usagerates of the some of nozzles E comprising the nozzle group E1. Thecontroller is configured to control the nozzle group E2 to eject fluidat an average usage rate E2 that is an average of usage rates of theothers of nozzles E comprising the nozzle group E2. The controller isconfigured to control the nozzle group F to eject fluid at an averageusage rate F that is an average of usage rates of the some of thenozzles F comprising the nozzle group F. The average usage rate A2 issmaller than the average usage rate A1. The average usage rate B1 issmaller than the average usage rate A1. The average usage rate C issmaller than the average usage rate A1. The average usage rate D2 issmaller than the average usage rate E2. The average usage rate E1 issmaller than the average usage rate E2. The average usage rate F issmaller than the average usage rate E2.

According to further aspect of the disclosure, a fluid ejectionapparatus includes a first head chip extending from a first end in afirst direction towards a second end in the first direction. The firsthead chip includes a nozzle row A comprising nozzles A arranged alongthe first direction, a nozzle row B comprising nozzles B arranged alongthe first direction, and a nozzle row C comprising nozzles C arrangedalong the first direction. The fluid ejection apparatus includes asecond head chip extending from a third end in the first directiontowards a fourth end in the first direction. The second head chipincludes a nozzle row D comprising a plurality of nozzles D arrangedalong the first direction, a nozzle row E comprising nozzles E arrangedalong the first direction, and a nozzle row F comprising nozzles Farranged along the first direction. The fluid ejection apparatusincludes a controller configured to control the first head chip and thesecond head chip to eject fluid from the first head chip and the secondhead chip. The nozzle row B is positioned between the nozzle row A andthe nozzle row D in a second direction orthogonal to the firstdirection. The nozzle row D is positioned between the nozzle row B andthe nozzle row E in the second direction. The nozzles A of the nozzlerow A are arranged into a nozzle group A1 and a nozzle group A2. Thenozzle group A1 comprises some of the nozzles A. The nozzle group A2comprises others of the nozzles A. The nozzle group A1 is positionedbetween the nozzle group A2 and the center of the first head chip in thefirst direction. The nozzles B of the nozzle row B are arranged into anozzle group B1. The nozzle group B1 comprises some of the nozzles B.The nozzle group A1 and the nozzle group B1 are aligned along the seconddirection. The nozzles C of the nozzle row C are arranged into a nozzlegroup C. The nozzle group C comprises some of the nozzles C. The nozzlegroup A2 and a portion of the nozzle group C are aligned along thesecond direction. The nozzles D of the nozzle row D are arranged into anozzle group D2. The nozzle group D2 of the nozzle row D comprises someof the nozzles D. The nozzle group A2 and the nozzle group D2 arealigned along the second direction. The nozzles E of the nozzle row Eare arranged into a nozzle group E1 and a nozzle group E2. The nozzlegroup E1 comprises some of the nozzles E. The nozzle group E2 comprisesothers of the nozzles E. The nozzle group A1 and the nozzle group E1 arealigned along the second direction. The nozzle group A2 and the nozzlegroup E2 are aligned along the second direction. The nozzles F of thenozzle row F are arranged into a nozzle group F. The nozzle group Fcomprises some of the nozzles F. The nozzle group A2 and a portion ofthe nozzle group F are aligned along the second direction. The nozzlegroup C and the nozzle group F are aligned along the second direction.The controller is configured to control the nozzle group A1 to ejectfluid at an average usage rate A1 that is an average of usage rates ofthe some of nozzles A comprising the nozzle group A1. The controller isconfigured to control the nozzle group A2 to eject fluid at an averageusage rate A2 that is an average of usage rates of the others of nozzlesA comprising the nozzle group A2. The controller is configured tocontrol the nozzle group B1 to eject fluid at an average usage rate B1that is an average of usage rates of the some of nozzles B comprisingthe nozzle group B1. The controller is configured to control the nozzlegroup C to eject fluid at an average usage rate C that is an average ofusage rates of the some of nozzles C comprising the nozzle group C. Thecontroller is configured to control the nozzle group D2 to eject fluidat an average usage rate D2 that is an average of usage rates of thesome of nozzles D comprising the nozzle group D2. The controller isconfigured to control the nozzle group E1 to eject fluid at an averageusage rate E1 that is an average of usage rates of the some of nozzles Ecomprising the nozzle group E1. The controller is configured to controlthe nozzle group E2 to eject fluid at an average usage rate E2 that isan average of usage rates of the others of nozzles E comprising thenozzle group E2. The controller is configured to control the nozzlegroup F to eject fluid at an average usage rate F that is an average ofusage rates of the some of the nozzles F comprising the nozzle group F.The average usage rate A2 is smaller than the average usage rate A1. Theaverage usage rate B1 is smaller than the average usage rate A1. Theaverage usage rate C is smaller than the average usage rate A1. Theaverage usage rate D2 is smaller than the average usage rate E2. Theaverage usage rate E1 is smaller than the average usage rate E2. Theaverage usage rate F is smaller than the average usage rate E2.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an inkjet printer in an illustrativeembodiment according to one or more aspects of the disclosure.

FIG. 2 is a plan view of an inkjet head of the inkjet printer accordingto one or more aspects of the disclosure.

FIG. 3 is a block diagram illustrating an electrical configuration ofthe inkjet printer according to one or more aspects of the disclosure.

FIG. 4A is a diagram illustrating intermediate ejection data accordingto one or more aspects of the disclosure.

FIG. 4B is a diagram illustrating ink drop deposition onto a recordingsheet according to one or more aspects of the disclosure.

FIG. 5 illustrates fluid ejection processing at a transition between twohead chips according to one or more aspects of the disclosure.

FIG. 6 illustrates a usage rate table according to one or more aspectsof the disclosure.

FIG. 7 is a flowchart of ejection data generating processing accordingto one or more aspects of the disclosure.

FIG. 8 is a diagram illustrating the ejection data generating processingaccording to one or more aspects of the disclosure.

FIG. 9 illustrates fluid ejection processing at a transition between twohead chips according to one or more aspects of the disclosure.

FIG. 10 illustrates another usage rate table according to one or moreaspects of the disclosure.

DETAILED DESCRIPTION

An illustrative embodiment and its modifications according to one ormore aspects of the disclosure are described in detail with reference tothe accompanying drawings. In the disclosure, a direction along aconveyance direction in which a recording sheet 100 is conveyed may bedefined as a front-rear direction of a printer 1, as labelled in FIG. 1.A width or lateral direction of the printer 1 perpendicular to theconveyance direction may be defined as a left-right direction of theprinter 1. A direction orthogonal to the front-rear direction and theleft-right direction and extending into the page of FIG. 1 may bedefined as a top-bottom or vertical direction of the printer 1.

<General Configuration of Printer>

As depicted in FIG. 1, the printer 1 includes a platen 3, an inkjet head4, two conveyance rollers 5 and 6, and a controller 7, which are housedinside a casing 2 of the printer 1.

An upper surface of the platen 3 supports a recording sheet 100 beingconveyed by the conveyance rollers 5 and 6. The conveyance rollers 5 and6 are disposed behind and in front of the platen 3, respectively. Eachof the conveyance rollers 5 and 6 is configured to be driven by aconveyance motor 8 (refer to FIG. 3). The rollers 5 and 6 may convey therecording sheet 100 toward the platen 3 or over the platen 3 in aforward direction.

The inkjet head 4 is disposed above the platen 3. The inkjet head 4 isconfigured to receive color inks (e.g., black, yellow, cyan, andmagenta) from ink tanks (not depicted). In one example, the inkjet head4 is capable of ejecting four colors of ink.

<General Configuration of Inkjet Head>

The inkjet head 4 is now described in detail. As depicted in FIG. 2, theinkjet head 4 includes four head chips 11 arranged in the left-rightdirection. The head chips 11 are held in a chip holder 10.

Two head chips 11 are disposed on a front side while the other two headchips 11 are disposed on a rear side. Each of the four head chips 11(e.g., the center thereof in the left-right direction) is disposed at adifferent position in the left-right direction. The four head chips 11are arranged in a staggered adjacency to one another in the left-rightdirection.

Each of the four head chips 11 has the same or similar configuration. Ahead chip 11 includes a nozzle zone 13 on a lower surface thereof. Thenozzle zone 13 has a plurality of nozzles 12 formed therein. In oneexample, multiple nozzles 12 are arranged along the left-right directionin the nozzle zone 13 into a nozzle row 14. The nozzle zone 13 includes,for example, four, nozzle rows 14. The four nozzle rows 14 are arrangedalong the conveyance direction.

The four nozzle rows 14 include nozzle rows 14Y, 14M, 14C and 14K. Thenozzle row 14Y is configured to eject yellow ink; the nozzle row 14M isconfigured to eject magenta ink; the nozzle row 14C is configured toeject cyan ink, and the nozzle row 14K is configured to eject black ink.Each of the four nozzle rows 14 is configured to eject a different colorof ink. Yellow, cyan, and magenta inks are primary color inks.

The nozzle rows 14Y, 14M, 14C, and 14K are arranged in this order froman upstream side in the conveyance direction (e.g., from the rear side).A pitch or spacing between adjacent nozzles 12 in the left-rightdirection may be the same in the nozzle rows 14Y, 14M, 14C and 14K.

The four head chips 11 include head chips 11 c 1, 11 c 2, 11 c 3, and 11c 4. The head chip 11 c 1 is disposed leftmost and on the rear side. Thehead chip 11 c 4 is disposed rightmost and on the front side. The headchip 11 c 2 is disposed on the front side and such that a center C2thereof in the left-right direction is positioned to the right of acenter C1 of the head chip 11 c 1 in the left-right direction. The headchip 11 c 3 is disposed on the rear side and such that a center C3thereof in the left-right direction is positioned to the left of acenter C4 of the head chip 11 c 4 in the left-right direction. Thecenter C2 of the head chip 11 c 2 is positioned to the left of thecenter C3 of the head chip 11 c 3.

The head chip 11 c 1 has a transitional zone AR1 at a right end portionof the nozzle zone 13 thereof. The head chip 11 c 2 has a transitionalzone AL2 at a left end portion of the nozzle zone 13 thereof. Each ofthe transitional zones AR1 and AL2 has the same number of the nozzles12. The head chips 11 c 1 and 11 c 2 are arranged such that thetransitional zones AR1 and AL2 are aligned along the conveyancedirection, defining an overlap head zone. The transitional zones AR1 andAL2 are aligned along the conveyance direction. The nozzles 12 of thenozzle rows 14 within the transitional zone AR1 of the head chip 11 c 1may align with the nozzles 12 of the nozzle rows 14 within thetransitional zone AL2 of the head chip 11 c 2, in the conveyancedirection. It is to be noted that manufacturing or assembling deviationsof the head chips 11 c 1 and 11 c 2 may cause the nozzles 12 in thetransitional zones AR1 and AL2 to be slightly misaligned from eachother.

The head chip 11 c 2 also has a transitional zone AR2 at a right endportion of the nozzle zone 13 thereof. The head chip 11 c 3 hastransitional zones AL3 and AR3, respectively, at left and right endportions of the nozzle zone 13 thereof. The head chip 11 c 4 has atransitional zone AL4 at a left end portion of the nozzle zone 13thereof. The relationship between the transitional zones AR1 and AL2,with respect to the number of the nozzles 12, positions of the nozzles12 in the left-right direction, and positional relation with respect tothe conveyance direction, is applied to the transitional zones AR2 andAL3, and the transitional zones AR3 and AL4.

The four head chips 11 are arranged such that the transitional zones oftwo head chips 11 (e.g., 11 c 1 and 11 c 2; 11 c 2 and 11 c 3; and 11 c3 and 11 c 4) are aligned along conveyance direction, defining anoverlap head zone. In other words, the transitional zones AR1 and AL2 ofthe head chips 11 c 1 and 11 c 2, respectively, define an overlap headzone; the transitional zones AR2 and AL3 of the head chips 11 c 2 and 11c 3, respectively, define another overlap head zone; and thetransitional zones AR3 and AL4 of the head chips 11 c 3 and 11 c 4,respectively, define still another overlap head zone. The four headchips 11, each having the evenly spaced nozzles 12 in the left-rightdirection, constitute one line head.

As depicted in FIG. 3, each of the head chips 11 includes an actuator 15and a driving device 16. The actuator 15 includes a plurality ofactuator elements for ejecting ink from the respective nozzles 12. Thedriving device 16 is configured to individually drive the actuatorelements. The actuator 15 is not limited to a specific type. In oneexample, the actuator 15 may be a piezoelectric actuator includingpiezoelectric elements as actuator elements. The piezoelectric elementsmay pressurize ink using deformation of a piezoelectric layer thereofwith inverse piezoelectric effect. In another example, an actuatorelement may be a heating element that generates bubbles in ink withheat. The driving device 16 is configured to perform digital-to-analogconversion of ejection data (to be described below) transmitted from thecontroller 7 into analog ejection signals. The driving device 16 isconfigured to output the ejection signals to the respective actuatorelements of the actuator 15.

<Configuration of Controller>

As depicted in FIG. 3, the controller 7 includes a central processingunit (“CPU”) 71, a read only memory (“ROM”) 72, a random access memory(“RAM”) 73, an interface (“I/F”) 74, a raster image processor (“RIP”)75, an image processing IC 76, a conveyance control IC 77, and arecording control IC 78.

The ROM 72 stores therein programs to be executed by the CPU 71 and theRIP 75. The RAM 73 is used as a work area for the CPU 71 and the RIP 75.

The I/F 74 allows for data communication with an external device 9,e.g., a personal computer (“PC”). For example, the I/F 74 may allow forimage data reception from the external device 9. The image data mayinclude data written, for example, in page description language (PDL).The RIP 75 is configured to perform a known raster image processing(RIP) for the image data received from the external device 9 to generateRGB data, which is represented by the RGB color system. The RGB data maybe bit map data in which red (R), green (G) and blue (B) color valueswith 256 levels are assigned to each pixel.

The image processing IC 76 is configured to generate intermediateejection data for each ink color based on the RGB data. In one example,the image processing IC 76 first performs color space conversion for theRGB data, to produce CMYK data. The CMYK data may be data in which cyan(C), magenta (M), yellow (Y), and black (K) color values with 256 levelsare assigned to each pixel. Cyan, magenta, yellow, and black are colorsof inks that are to be ejected from the inkjet head 4. Subsequently, theimage processing IC 76 executes, for example, a known error diffusionprocessing for quantizing the CMYK data, to generate intermediateejection data with lower level for each ink color, as depicted in FIG.4A. For example, the CMYK data may be quantized into two levels if theprinter 1 is capable of recording an image with two levels, or into fourlevels if the printer 1 is capable of recording an image with fourlevels. FIG. 4A illustrates intermediate ejection data for cyan in twolevels. In the matrix, the letter C represents a pixel for which cyanink is to be ejected, and a pixel for which no cyan ink is to be ejectedis shown without any letter. FIG. 4A illustrates nine rows or lines ofraster data, each including nine pixels.

As can be seen from FIG. 4A, the intermediate ejection data includes aplurality of rows or lines of raster data. The raster data for one lineis an array of a plurality of pixels, each pixel corresponding to arespective one of dots to be arranged on the recording sheet 100 in theleft-right direction. The dots include such dots that require no inkejection.

The conveyance control IC 77 is configured to control the conveyancemotor 8 to cause the conveyance rollers 5 and 6 to convey the recordingsheet 100 in the conveyance direction.

The recording control IC 78 is configured to generate ejection data foreach of the four head chips 11, based on the intermediate ejection datafor each color generated by the image processing IC 76. The recordingcontrol IC 78 is configured to generate ejection data for executingejection processing to eject four colors of ink from the head chips 11,based on the ejection data. The ejection processing is performed in astate in which the recording sheet 100 facing the head chips 11 is beingconveyed, to record an image on the recording sheet 100.

For the ejection processing, the controller is configured to generateejection data for controlling ejection times for the nozzle rows 14 suchthat each of primary color inks (e.g., yellow, magenta, and cyan inks)is able to be deposited alone or overlapping another primary color inkat a primary color ink landing position. The primary color ink landingposition is different from the landing positions of the black ink (asdepicted in FIG. 4B). The primary color ink landing position may receivea single or combination of the primary color inks. In one example, alanding or deposition position of ink ejected from at least one of thenozzle rows 14Y, 14M, and 14C on the recording sheet 100 may bedifferent, with respect to the conveyance direction, from a landing ordeposition position of ink ejected from the nozzle row 14K on therecording sheet 100.

A reason for this is to prevent reduction in saturation of a mixedcolor, which is formed by mixing any primary colors cyan, yellow, andmagenta. Mixture of primary colors creates mixed colors, e.g., secondarycolors and tertiary colors, such as red, blue, and green. Black is alowest brightness color. Accordingly, black may reduce saturation ofmixed colors, even with a small amount. To maintain saturation of mixedcolors, it may be preferable that black ink may be deposited on aposition of the recording sheet 100 different to that of each of theprimary color inks, which may be components of a mixed color. Whenmultiple colors are mixed to create a specific color, a color of inkthat is deposited first on the sheet 100 is likely to be dominant If aprimary color ink is deposited over black ink on the sheet 100, theprimary color ink may turn into a darker color. Black is the lowestcolor with respect to brightness, as described above, so that thebrightness of the primary color ink deposited over black ink may besignificantly reduced. This may result in an improper mixed colorcreation. In other words, black ink deposited on a position of the sheet100 different from a position of each of the primary color inks mayprevent significant reduction in brightness of the primary color inks,leading to proper mixed color creation.

For example, the printer 1 may use pigment ink for black to place anemphasis on text and lines (e.g., for appealing to the eye), and dye inkfor other colors (e.g., primary colors) to increase saturation. If aprimary color ink is deposited overlapping black ink, saturation ofpigment black ink may be reduced, resulting in unappealing text andlines. Accordingly, to emphasize text and lines with black pigment ink,it may be preferable to deposit black ink at a different position on thesheet 100 to that of each of the primary color inks.

For the above reason, the recording control IC 78 generates ejectiondata for controlling ejection times of the respective nozzle rows 14 toalternate a black ink dot and a primary color ink dot along theconveyance direction of the recording sheet 100. Such controlling isdescribed in detail below with reference to FIG. 4B.

In FIG. 4B, the letter K represents a landing or deposition position ofblack ink on the recording sheet 100. The letter P represents a landingor deposition position of at least two different primary color inks ofyellow, cyan, and magenta. In the illustrative embodiment, inks ofmultiple primary colors yellow, cyan, and magenta may be deposited on alanding position P. In another example, ink of one primary color may bedeposited in a landing position P. The number N following the letter Por K corresponds to the “N”th line of raster data. For example, “K2”represents a landing position of black ink ejected based on a pixel ofthe second line of raster data.

With respect to landing positions of primary color inks deposited on therecording sheet 100 based on a corresponding or the same line of rasterdata of ejection data for the respective colors, the recording controlIC 78 generates ejection data for controlling the inkjet head 4 suchthat a landing position of one of the primary color inks aligns in thenozzle arranging direction. In one example, with respect to acorresponding line of raster data in the respective color ejection data,the recording control IC 78 generates ejection data for controllingejection times of inks from the nozzle rows 14Y, 14M, and 14C such thata first ejection time interval, a second ejection time interval, and athird ejection time interval becomes a first particular time interval.The first ejection time interval is a temporal ink ejection intervalbetween the nozzle rows 14Y and 14M. The second ejection time intervalis a temporal ink ejection interval between the nozzle rows 14M and 14C.The third ejection time interval is a temporal ink ejection intervalbetween the nozzle rows 14Y and 14C. The first particular time intervalis a temporal interval obtained by dividing a distance in the conveyancedirection between two nozzle rows to be used, by a conveying speed ofthe recording sheet 100. The distance between the two nozzle rows to beused may be, for example, a distance between the nozzle rows 14Y and14M; a distance between the nozzle rows 14M and 14C; and a distancebetween the nozzle rows 14Y and 14C. Inks of any two of yellow, cyan andmagenta may be deposited at the same or one position to form a secondarycolor ink dot on the recording sheet 100, or all of three colors may bedeposited at the same or one position to form a tertiary color ink doton the sheet 100.

For example, assuming that ink is ejected from the nozzle rows 14C and14K, the recording control IC 78 generates ejection data for controllingejection times of inks from the respective nozzle rows 14C and 14K inthe following matter. For example, with respect to the same orcorresponding line of respective cyan and black raster data, therecording control IC 78 generates ejection data for controlling ejectiontimes of inks from the nozzle rows 14C and 14K such that a fourthejection time interval becomes a second particular time interval. Thefourth ejection time interval is a temporal ink ejection intervalbetween the nozzle rows 14C and 14K. The second particular time intervalis a temporal interval obtained by dividing a distance in the conveyancedirection between the nozzle rows 14C and 14K, to which a predetermineddistance is added, by a conveying speed of the recording sheet 100. Thepredetermined distance is a distance corresponding to a shifted amountin the conveyance direction between a black dot and its adjacent dotformed by primary color inks on the recording sheet 100. Thepredetermined distance is shorter than a distance in the conveyancedirection between two dots formed on the recording sheet 100 with agiven nozzle 12 based on two consecutive lines of raster data.Accordingly, when inks are ejected from the respective nozzle rows 14Y,14M, 14C, and 14K based on a corresponding line of the respective rasterdata, a landing position of black ink does not overlap a landingposition of each primary color ink on the recording sheet 100.

(Ejection Processing at Transitional Zones)

Next, ejection processing for ejecting ink from the nozzles 12 intransitional zones is described with reference to FIG. 5. Ejection datafor the ejection processing is generated by the recording control IC 78.In FIG. 5, solid circles denote the nozzles 12 to be used in theejection processing and open circles denote the nozzles 12 to be unusedin the ejection processing. Ink ejection from, for example, the headchips 11 c 1 and 11 c 2, will be described below. A lower portion inFIG. 5 illustrates, in graphs, usage rates of the nozzles 12 of therespective nozzle rows 14Y, 14M, 14C, and 14K of the head chips 11 c 1and 11 c 2.

Before discussing the ejection processing in further detail, it will behelpful for understanding aspects of the disclosure to briefly discussprint density unevenness caused by, for example, the head chips 11 c 1and 11 c 2. An portion of the recording sheet 100 corresponding to anoverlap head zone (e.g., defined by the transitional zones AR1 and AL2)may be referred to as the “portion A” of the recording sheet 100 andother portion of the recording sheet 100 corresponding to other zone ofthe head chips 11 c 1 and 11 c 2 than the overlap head zone(s) may bereferred to as a “portion B” of the recording sheet 100. The head chips11 c 1 and 11 c 2 may have nozzles 12 with different ejectioncharacteristics between the head chips 11 c 1 and 11 c 2. The head chips11 c 1 and 11 c 2 may also have assembling deviation. These may causelanding position misalignment of inks ejected from the nozzles 12 in thetransitional zones AR1 and AL2, resulting in print density unevenness.

To reduce the print density unevenness, nozzles 12 of a nozzle row 14 inthe transitional zone AR1 may be switched to nozzles 12 of acorresponding nozzle row 14 in the transitional zone AL2, such that thenozzles 12 of the nozzle rows 14 in the transitional zones AR1 and AL2are used complementary to each other.

This solution may reduce but not eliminate print density unevenness. Asdescribed above, each of at least two inks of yellow, magenta, and cyanmay be deposited at the same one position on the recording sheet 100 toform a dot of mixed color, e.g., secondary color and tertiary color.This may cause print density unevenness to be more noticeable in animage formed by the nozzles 12 in the transitions AR1 and AL2 (e.g., inthe portion A of the sheet 100), because the print density unevennesscaused by the respective color inks forming the mixed color may buildup. Accordingly, print density unevenness in an image between theportion A and the portion B of the recording sheet 100 may benoticeable.

Discussing now the ejection processing in detail with reference to FIG.5, each of the transitional zones AR1 and AL2 is divided into threesub-zones a1, a2, and a3. The sub-zones a1, a2, and a3 correspond to thenozzle rows 14C, 14M, and 14Y, respectively. Each of the sub-zones a1,a2, and a3 is located at a position different from one another in theleft-right direction without overlapping one another. A width of each ofthe sub-zones a1, a2, and a3 in the left-right direction is the same,and each sub-zone a1, a2, and a3 has the same number of the nozzles 12therein.

In operation, the nozzles 12 of the respective nozzle rows 14C, 14M, and14Y may be switched from a head chip 11 c 1 to another head chip 11 c 2at a corresponding sub-zones a1, a2, and a3.

In one example, the recording control IC 78 is configured to generateejection data for executing the ejection processing in which the nozzles12 of the nozzle row 14C in the sub-zone a1 of the head chip 11 c 1 andthe counterpart of the head chip 11 c 2 (e.g., the nozzles 12 of thenozzle row 14C in the sub-zone a1 of the head chip 11 c 2) are usedcomplementary to each other at respective predetermined usage rates. Therecording control IC 78 is also configured to generate ejection data forexecuting the ejection processing in which the nozzles 12 of the nozzlerow 14M in the sub-zone a2 of the head chip 11 c 1 and the counterpartof the head chip 11 c 2 (e.g., the nozzles 12 of the nozzle row 14M inthe sub-zone a2 of the head chip 11 c 2) are used complementary to eachother at respective predetermined usage rates. Similarly, the recordingcontrol IC 78 is configured to generate ejection data for executing theejection processing in which the nozzles 12 of the nozzle row 14Y in thesub-zone a3 of the head chip 11 c 1 and the counterpart of the head chip11 c 2 (e.g., the nozzles 12 of the nozzle row 14Y in the sub-zone a3 ofthe head chip 11 c 2) are used complementary to each other at respectivepredetermined usage rates.

A usage rate indicates a ratio of the nozzles 12 to be used in the headchips 11 c 1 and 11 c 2. In other words, the usage rate indicates howmany dots (including non-ejection dot) are formed in a predeterminedarea of the recording sheet 100 by the nozzles 12 of which the head chip11 c 1 or 11 c 2. For example, it is assumed that ten (10) dots are tobe formed in an area of the recording sheet 100 based on the ejectiondata and the usage rate of the head chip 11 c 1 for that area is, forexample, 70%. In this case, seven dots out of ten are to be formed bythe nozzles 12 of the head chip 11 c 1 while the other three dots are tobe formed by the nozzles 12 of the head chip 11 c 2.

As can been seen from the graph in FIG. 5, which shows the usage ratesof the nozzle rows 14C of the head chips 11 c 1 and 11 c 2, a usage rateof the nozzles 12 of the nozzle row 14C of the head chip 11 c 1 to theleft of the sub-zone a1 is 100%. A usage rate of the nozzles 12 of thenozzle row 14C of the head chip 11 c 2 to the right of the sub-zone a1is 100%.

In the sub-zones a1, the usage rates of the nozzle rows 14C changelinearly. In one example, the usage rate of the nozzles 12 of the headchip 11 c 1 gradually decreases from left to right, while the usage rateof the nozzles 12 of the head chip 11 c 2 gradually increases from leftto right. The usage rates of the nozzles 12 of the head chips 11 c 1 and11 c 2 thus gradually change. This gradual change in the usage rates forthe nozzle rows 14C between the head chips 11 c 1 and 11 c 2 may reduceprint density unevenness in an image formed on the recording sheet 100(e.g., in the portion A) with the nozzles 12 of the nozzle rows 14C inthe sub-zones a1, even if there are differences in ejectioncharacteristics or performances between the nozzles 12 of the head chips11.

The recording control IC 78 is configured to generate ejection data forexecuting the ejection processing in which the nozzles 12 of the nozzlerow 14M at the sub-zone a2 of the head chip 11 c 1 and the counterpartof the head chip 11 c 2 are used complementary to each other atrespective predetermined usage rates. As can been seen from the graph inFIG. 5, the usage rates of the nozzle rows 14M of the head chips 11 c 1and 11 c 2 change linearly in the sub-zones a2.

The recording control IC 78 is configured to generate ejection data forexecuting the ejection processing in which the nozzles 12 of the nozzlerow 14Y at the sub-zone a3 of the head chip 11 c 1 and the counterpartof the head chip 11 c 2 are used complementary to each other atrespective predetermined usage rates. As can been seen from the graph inFIG. 5, the usage rates of the nozzle rows 14Y of the head chips 11 c 1and 11 c 2 change linearly in the sub-zones a3.

Thus, the recording control IC 78 generates the ejection data forcontrolling the use of the nozzles 12 of each of the nozzle rows 14Y,14M, and 14C to be switched from the head chip 11 c 1 to the head chip11 c 2 at a corresponding sub-zone a1-a3 of the transitional zones AR1and AL2. This may reduce buildup or accumulation of print densityunevenness of yellow, magenta, and cyan inks on the recording sheet 100.

As mentioned above, a landing position of black ink on the recordingsheet 100 is different from that of each of other three primary colorinks. Accordingly, print density unevenness on the recording sheet 100caused by black ink may not overlap with print density unevenness causedby the primary color inks. Accordingly, use of the nozzles 12 of thenozzle rows 14K does not necessarily be switched from the head chip 11 c1 to the head chip 12 c at a zone other than the sub-zones a1, a2, anda3.

A sub-zone a4 overlaps with the sub-zones a1, a2, a3 in the left-rightdirection. The sub-zone a4 is a zone where use of the nozzles 12 of thenozzle rows 14K may be switched from the head chip 11 c 1 to the headchip 11 c 2. The recording control IC 78 is configured to generateejection data for executing the ejection processing in which the nozzles12 of the nozzle row 14K in the sub-zone a4 of the head chip 11 c 1 andthe counterpart of the head chip 11 c 2 (e.g., the nozzles 12 of thenozzle row 14K in the sub-zone a4 of the head chip 11 c 2) are usedcomplementary to each other at respective predetermined usage rates.

The sub-zone a4 overlaps with the sub-zones a1, a2, and 3. Thisarrangement may reduce the width of the transitional zone in theleft-right direction as compared with a case in which the sub-zone a4 isprovided at a position different from the sub-zones a1, a2, and a3.Accordingly, the width of the transitional zone AR1 of the head chip 11c 1 or the transitional zone AL2 of the head chip 11 c 2 in theleft-right direction may be reduced. This may reduce the number of thehead chips 11 required to constitute one line head that extends apredetermined length in the left-right direction.

As can be seen from the graph of FIG. 5, which shows the usage rates ofthe nozzle rows 14K, the usage rates of the nozzle rows 14K changelinearly in the sub-zones a4. The sub-zone a4 is wider than each of thesub-zones a1, a2, and a3. Accordingly, the slope of the graph indicatingchanges in the usage rates of the nozzle rows 14K is not as steep as theslopes of the graphs indicating changes in the usage rates of othernozzle rows 14Y, 14M, and 14C. This may reduce print density unevennessof an image formed on the recording sheet 100 (e.g., in the portion A)with the nozzles 12 of the nozzle rows 14K in the transitional zones a4of the head chips 11 c 1 and 11 c 2.

(Controls for Ink Landing/Deposition Sequence)

Each of yellow, cyan, and magenta inks deposited at one same position onthe recording sheet 100 may form a secondary or tertiary color dot. Theresulting color of the dot may be perceived by the human eye differentlydepending on landing or deposition sequences of the inks.

For example, it is assumed that yellow and cyan inks are deposited oroverlaid at the same position to form a dot of secondary color green.Hue of a dot formed on the recording sheet 100 by the deposition ofyellow ink first, and then cyan ink may be different from hue of a dotformed on the recording sheet 100 by the deposition of cyan ink first,and then yellow ink.

Taking the head chips 11 c 1 and 11 c 2 as an example, the arrangementof the nozzle rows 14Y, 14M, and 14C in the conveyance direction isdifferent between portions of the head 4 where the transitional zonesAR1 and AL2 are provided and are not provided. At a portion of the head4 where the transitional zones AR1 and AL2 are aligned in the conveyancedirection, the nozzles rows 14Y, 14M, and 14C are arranged in theconveyance direction from the upstream side in the conveyance direction,in the order of the nozzle row 14Y (of the head chip 11 c 1); the nozzlerow 14M (of the head chip 11 c 1); the nozzle row 14C (of the head chip11 c 1); the nozzle row 14Y (of the head chip 11 c 2); the nozzle row14M (of the head chip 11 c 2); and the nozzle row 14C (of the head chip11 c 2). At a portion of the head 4 where the transitional zones AR1 andAL2 are not provided, the nozzle rows 14Y, 14M, and 14C are arranged inthe conveyance direction from the upstream side in this order. This maycreate differences in the landing/deposition sequences of the primarycolor inks when a dot of a mixed color is formed by depositing at leasttwo of yellow, cyan, and magenta inks at one same position on therecording sheet 100. Consequently, dots of inks ejected from the nozzles12, which are within the transitional zones AR1 and AL2 and which arenot within the zones AR1 and AL2, may cause hue difference, resulting ina degraded image quality on the recording sheet 100.

With respect to the nozzle rows 14Y, 14M, and 14C, each sub-zone a1-a3of the head chips 11 c 1 and 11 c 2 has a sub-zone corresponding nozzlerow (e.g., the nozzle row 14C for the sub-zone a1) and sub-zonenoncorresponding nozzle rows (e.g., the nozzle rows 14M and 14Y for thesub-zone a1). The sub-zone corresponding nozzle row corresponds to therespective one of the sub-zones a1-a3. The sub-zone noncorrespondingnozzle rows are the nozzle rows within each of the sub-zones a1-a3 otherthan the sub-zone corresponding nozzle row. The sub-zone a1 of the headchip 11 c 1 and the sub-zone a1 of the head chip 11 c 2 define a firstoverlap sub-zone. Similarly, the sub-zones a2 of the head chips 11 c 1and 11 c 2 define a second overlap sub-zone and the sub-zones a3 of thehead chips 11 c 1 and 11 c 2 define a third overlap sub-zone. In eachoverlap sub-zone, the nozzles 12 of sub-zone noncorresponding nozzlerows of either one of the head chips 11 c 1 and 11 c 2 are used. Oneexample uses the nozzles 12 of sub-zone noncorresponding nozzle rows,which are not sandwiched between the sub-zone corresponding nozzle rowsof the head chips 11 c 1 and 11 c 2.

For example, with respect to the sub-zones a1 of the head chips 11 c 1and 11 c 2 (e.g., the first overlap sub-zone), the nozzle rows 14C arethe sub-zone corresponding nozzle rows, among the nozzle rows 14Y, 14M,and 14C, whereas the nozzles rows 14Y and 14M are sub-zonenoncorresponding nozzle rows. In the sub-zones a1 (e.g., the firstoverlap sub-zone), the nozzle rows 14Y and 14M of the head chip 11 c 2are sandwiched between the nozzle rows 14C of the respective head chips11 c 2 and 11 c 1. In contrast, the nozzle rows 14Y and 14M of the headchip 11 c 1 are not sandwiched between the nozzle rows 14C of therespective head chips 11 c 2 and 11 c 1. Accordingly, with respect tothe sub-zones a1 (e.g., the first overlap sub-zone), the nozzles 12 ofthe nozzle rows 14Y and 14M of the head chip 11 c 1 are used while thenozzles 12 of the nozzle rows 14Y and 14M of the head chip 11 c 2 arenot.

For example, with respect to the sub-zones a2 of the head chips 11 c 1and 11 c 2 (e.g., the second overlap sub-zone), the nozzle rows 14M arethe sub-zone corresponding nozzle rows among the nozzle rows 14Y, 14M,and 14C, whereas the nozzle rows 14Y and 14C are the sub-zonenoncorresponding nozzle rows. In the sub-zones a2 (e.g., the secondoverlap sub-zone), the nozzle row 14Y of the head chip 11 c 2 and thenozzle row 14C of the head chip 11 c 1 are sandwiched between the nozzlerows 14M of the respective head chips 11 c 2 and 11 c 1. In contrast,the nozzle row 14Y of the head chip 11 c 1 and the nozzle row 14C of thehead chip 11 c 2 are not sandwiched between the nozzle rows 14M of therespective head chips 11 c 2 and 11 c 1. Accordingly, with respect tothe sub-zones a2 (e.g., the second overlap sub-zone), the nozzles 12 ofthe nozzle row 14Y of the head chip 11 c 1 and the nozzles 12 of thenozzle row 14C of the head chip 11 c 2 are used while the nozzles 12 ofthe nozzle row 14C of the head chip 11 c 1 and the nozzles 12 of thenozzle row 14Y of the head chip 11 c 2 are not.

For example, with respect to the sub-zones a3 of the head chips 11 c 1and 11 c 2 (e.g., the third overlap sub-zone), the nozzle rows 14Y arethe sub-zone corresponding nozzle rows among the nozzle rows 14Y, 14M,and 14C, whereas the nozzle rows 14M and 14C are the sub-zonenoncorresponding nozzle rows. In the sub-zones a3 (e.g., the thirdoverlap sub-zone), the nozzle rows 14M and 14C of the head chip 11 c 1are sandwiched between the nozzle rows 14Y of the respective head chips11 c 2 and 11 c 11. In contrast, the nozzle rows 14M and 14C of the headchip 11 c 2 are not sandwiched between the nozzle rows 14Y of therespective head chips 11 c 2 and 11 c 1. Accordingly, with respect tothe sub-zones a3 (e.g., the third overlap sub-zone), the nozzles 12 ofthe nozzle rows 14M and 14C of the head chip 11 c 2 are used while thenozzles 12 of the nozzle rows 14M and 14C of the head chip 11 c 1 arenot.

In the sub-zones a1-a3 of the head chips 11 c 1 and 11 c 2 (e.g. in eachof the first, second and third overlap sub-zones), the inklanding/deposition sequence of the primary colors is first yellow, thenmagenta, and lastly cyan. In other words, the ink landing/depositionsequence of the primary colors in the transitional zones AR1 and AL2 issame as the ink deposition sequence of the primary colors in other zoneof the head chips 11 c 1 and 11 c 2 than the transitional zones AR1 andAL2. This may prevent or reduce changes or difference in hue between theportion A and the portion B of the recording sheet 100.

(Ejection Data Generating Processing)

Next, ejection data generating processing for the nozzles 12 in thetransitional zones AR1 and AL2 of the head chips 11 c 1 and 11 c 2,respectively, is described with reference to FIGS. 6-8. FIG. 8schematically illustrates only the nozzle rows 14C of the head chips 11c 1 and 11 c 2. Each of the transitional zones AR1 and AL2 of the headchips 11 c 1 and 11 c 2 has, for example, sixty (60) nozzles 12, in eachnozzle row 14.

The recording control IC 78 includes a memory 78 a (in FIG. 3) thatstores a usage rate table as depicted in FIG. 6. This table shows usagerates of the nozzles 12 in the respective transitional zones (e.g.,sub-zones) of the head chips 11 (e.g., the head chips 11 c 1 and 11 c 2)according to the nozzles rows 14. In ejection data generatingprocessing, ejection data for each of the head chips 11 c 1 and 11 c 2(e.g., two pieces of ejection data) may be generated with reference tothe usage rate table. For the purpose of description, the usage ratetable in FIG. 6 shows usage rates of the nozzles 12 in non-transitionalzones of the head chips 11 c 1 and 11 c 2. The non-transitional zonesare portions of the nozzle zones 13 of the respective head chips 11 c 1and 11 c 2 other than the transitional zones AR1 and AR2.

As depicted in FIG. 8, the sub-zone a1 is divided into, for example,five sections, in the left-right direction. Although not illustrated,each of the sub-zones a2 and a3 is also divided into, for example, fivesections, in the left-right direction. Each section of the sub-zonesa1-a3 has the same number of the nozzles 12, e.g., four nozzles. Thesub-zone a4 is divided into, for example, fifteen (15) sections, in theleft-right direction. The five sections from left out of the fifteensections overlap or correspond to the five sections of the sub-zone a1in the left-right direction. The five sections from right overlap orcorrespond to the five sections of the sub-zone a3 in the left-rightdirection. The remaining five sections, which are centrally located inthe left-right direction, overlap or correspond to the five sections ofthe sub-zone a2. Each of the fifteen (15) sections has the same width inthe left-right direction, and has the same number of the nozzles 12,e.g., four.

The usage rate table specifies usage rates of the nozzles 12 for each ofthe sections of the sub-zones a1-a4 according to the nozzle rows 14,such that the usage rates linearly change in each of the sub-zonesa1-a4. For example, with respect to the nozzle row 14C of the head chip11 c 1, the usage rates of the five sections of the sub-zone a1 arespecified as 100%, 75%, 50%, 25%, and 0%, from the leftmost sections. Incontrast, with respect to the nozzle row 14C of the head chip 11 c 2,the usage rates of the five sections of the sub-zone a1 are specified as0%, 25%, 50%, 75%, and 100%, from the leftmost section. Accordingly,with respect to sub-zone corresponding nozzle rows corresponding tosub-zones of the head chips 11 c 1 and 11 c 2, usage rates of nozzlesgradually change between sections of the sub-zones.

In the sub-zones a1-a3 (e.g., in each of the first to third overlapsub-zones), the usage rate of each of the sub-zone noncorrespondingnozzle rows, which are not sandwiched between the sub-zone correspondingnozzle rows of the head chips 11 c 1 and 11 c 2, is 100% in eachsection. In the sub-zones a1-a3 (e.g., in each of the first to thirdoverlap sub-zones), the usage rate of each of the sub-zonenoncorresponding nozzle rows, which are sandwiched between the sub-zonecorresponding nozzle rows of the head chips 11 c 1 and 11 c 2, is 0% ineach section. For example, the usage rates of the nozzle rows 14Y and14M at the five sections of the sub-zone a1 of the head chip 11 c 1 arespecified as 100%, whereas the usage rates of the nozzle rows 14Y and14M at the five sections of the sub-zone a1 of the head chip 11 c 2 arespecified as 0%.

Next, flow of ejection data generating processing to be executed by therecording control IC 78 is described. The ejection data generatingprocessing is now described in conjunction with the nozzles 12 of thenozzle rows 14C in the sub-zones a1 (e.g., in the first overlapsub-zone). Ejection data generating processing for the nozzles 12 ofother nozzle rows 14Y and 14M in the sub-zones a1 is basically the sameas the ejection data generating processing the nozzles 12 of the nozzlerows 14C in the sub-zones a1. Further, ejection data generatingprocessing for the nozzle rows 14C, 14Y and 14M of other sub-zones a2and a3, as well as for the nozzle rows 14K in the sub-zones a4, isbasically the same as the ejection data generating processing for thenozzles 12 of the nozzle rows 14C in the sub-zones a1.

As depicted in FIG. 7, for each of the head chips 11 c 1 and 11 c 2, therecording control IC 78 extracts twenty (20) pixels from one line ofraster data of ejection data for cyan ink (S1). The twenty (20) pixelscorrespond to the twenty (20) nozzles 12 provided in the sub-zone a1. Ascan be seen from FIG. 8, the twenty pixels extracted in correspondencewith the twenty nozzles 12 in the sub-zone a1 include pixels thatrequire ink ejection (e.g., pixels represented by the letter “C”s inboxes in FIG. 8), as well as pixels that do not require ink ejection(e.g., pixels with no letter in boxes in FIG. 8).

Subsequently, the recording control IC 78 loads the twenty pixelsextracted at S1 into the RAM 73, in correspondence with the twentynozzles 12 of the nozzle row 14C in the sub-zone a1 of the head chip 11c 1 (S2). Similarly, the recording control IC 78 loads the twenty pixelsextracted at S1 into the RAM 73, in correspondence with the twentynozzles 12 of the nozzle row 14C in the sub-zone a1 of the head chip 11c 2 (S2). Accordingly, the number of pixels corresponding to thesub-zones a1 is forty (40) in total. Subsequently, the recording controlIC 78 reads the usage rates specified for the sections of the sub-zonesa1 for the nozzle rows 14C, from the usage rate table stored in thememory 78 a (S3).

Subsequently, the recording control IC 78 performs masking, inaccordance with the usage rates read at S3, on the respective sets oftwenty pixels (40 pixels in total) loaded at S2 into the RAM 73 (S4). Inone example, the recording control IC 78 performs masking on the twentypixels corresponding to the nozzles 12 of the nozzle row 14C in thesub-zone a1 of the head chip 11 c 1 and another twenty pixelscorresponding to the nozzles 12 of the nozzle row 14C in the sub-zone a1of the head chip 11 c 2, based on usage rates specified for sections ofthe respective sub-zones a1.

At S4, the recording control IC 78 generates a mask pattern for each ofthe head chips 11 c 1 and 11 c 2, based on the usage rates specified forthe sections of the sub-zones a1. The mask patters for head chips 11 c 1and 11 c 2 are complementary to each other, with respect to a particularsection of the head chip 11 c 1 and its corresponding section of thehead chip 11 c 2. The recording control IC 78 ANDs data constituted bythe twenty pixels for the head chip 11 c 1, which are loaded into theRAM 73 at S2, with the mask pattern for the head chip 11 c 1. Theresulting data is the ejection data for the nozzles 12 of the nozzle row14C in the sub-zone a1 of the head chip 11 c 1. Similarly, the recordingcontrol IC 78 ANDs data constituted by the twenty pixels for the headchip 11 c 2, which are loaded into the RAM 73 at S2, with the maskpattern for the head chip 11 c 2. The resulting data is the ejectiondata for the nozzles 12 of the nozzle row 14C in the sub-zone a1 of thehead chip 11 c 2.

The recording control IC 78 outputs the ejection data for the head chips11 c 1 and 11 c 2 to the driving device 16. This enables the nozzles 12of the nozzle rows 14C in the sub-zones a1 of the respective head chips11 c 1 and 11 c 2 to be used complementary. To prevent particularnozzles 12 in the sub-zones a1 from being unused for a long period oftime, it may be preferable to use another mask pattern for everypredetermined number of lines of raster data while the usage rates forthe respective sections are maintained.

Two pieces of the ejection data, one for twenty pixels corresponding tothe nozzles 12 of the head chip 11 c 1 and the other for another twentypixels corresponding to the nozzles 12 of the head chip 11 c 2, may begenerated without mask patterns. For example, based on unused periods ofthe nozzles 12 in the respective sub-zones a1 of the head chips 11 c 1and 11 c 2, the recording control IC 78 may generate a piece of ejectiondata for the twenty nozzles 12 of each of the head chips 11 c 1 and 11 c2, in accordance with the usage rates, such that the nozzles 12 whichhave longer unused periods may be used preferentially.

The illustrative embodiment is described in conjunction with an examplein which ink is ejected from the head chips 11 c 1 and 11 c 2. Aspectsof the disclosure may be applied to other examples in which ink isejected from the head chips 11 c 2 and 11 c 3, as well as from the headchips 11 c 3 and 11 c 4. Such examples may also reduce print densityunevenness of an image formed on the recording sheet 100. For example,an example where ink is ejected from the head chips 11 c 2 and 11 c 3will be briefly described referring to FIG. 9. A significant differencefrom the above-described illustrative embodiment is a reversed arrangingdirection of the sub-zones a1-a3 in the left-right direction. In thisexample, the sub-zones a1-a3 are arranged in this order from right toleft. Except the arranging direction of the sub-zones a1-a3, ink may beejected from the head chips 11 c 2 and 11 c 3 in a similar manner to theexample in which ink is ejected from the head chips 11 c 1 and 11 c 2.Ink may be ejected from the head chips 11 c 3 and 11 c 4 basically inthe same manner to the example in which ink is ejected from the headchips 11 c 1 and 11 c 2.

As described above, the sub-zones a1-a3 are disposed at differentpositions from one another in the left-right direction. The use of thenozzles 12 of the nozzle rows 14C, 14Y, and 14M is switched from thehead chip 11 c 1 to the head chip 11 c 2 at the corresponding thesub-zones a1-a3. This may reduce degradation of quality of an image,which is caused by ink deposited on the recording sheet 100 in differingorders from the respective nozzle rows 14C, 14Y, and 14M. The sub-zonea4 overlaps with the sub-zones a1-a3 in the left-right direction. Thisarrangement may reduce a width in the left-right direction of, forexample, each of the transitional zones AR1 and AL2 of the head chips 11c 1 and the head chip 11 c 2, respectively. Further, the recordingcontrol IC 78 generates ejection data for controlling ink ejection timessuch that color ink from the respective nozzle rows 14C, 14Y, and 14Mmay be deposited onto the recording sheet 100 at a location differentfrom black ink from the nozzle row 14K in the conveying direction. Thismay reduce degradation of a quality of an image recorded on therecording sheet 100 even if the sub-zone a4 overlaps with the sub-zonesa1-a3 in the left-right direction.

The sub-zone a4 overlaps with all of the three sub-zones a1-a3 in theleft-right direction. This may allow the sub-zone a4 to have a widerwidth in the left-right direction. Consequently, occurrence of printdensity unevenness caused by ink ejected, for example, from the nozzlerows 14K of the head chips 11 c 1 and 11 c 2, on the recording sheet 100may be reduced.

With the ejection data generation by the recording control IC 78 asdescribed above, primary color inks may be ejected in the same sequencefrom the nozzles 12 in the transitional zones AR1 and AL2 of the headchips 11 c 1 and 11 c 2 (e.g., the overlap head zone) and the nozzles 12in other zone of the head chips 11 c 1 and 11 c 2 than the transitionalzones AR1 and AL2. This may reduce difference in resulting hue of animage on the recording sheet 100 between the portion A and the portionB.

As described above, each of the sub-zones a1-a4 includes a plurality ofsections arranged along the left-right direction. With respect to usagerates of sub-zone corresponding nozzle rows corresponding to sub-zonesof, for example, the head chips 11 c 1 and 11 c 2, the recording controlIC 78 generates two pieces of ejection data in which the usage rates aregradually changed between the sections. Accordingly, print densityunevenness of an image on the recording sheet 100 may be less noticeableeven if there are differences in ejection characteristics orperformances in the nozzles 12 of the head chips 11 c 1 and 11 c 2.

In the above-described description, the printer 1 is an example of afluid ejection apparatus. The inkjet head 4 is an example of a fluidejection head. The left-right direction is an example of a nozzlearranging direction. The conveyance direction is an example of arelative moving direction. Any two of the nozzle rows 14Y, 14M, and 14Care examples of a first nozzle row and a second nozzle row. The nozzlerow 14K is an example of a third nozzle row. Any two of the threesub-zones a1-a3 are examples of a first sub-zone and a second sub-zone.The sub-zone a4 is an example of a third sub-zone.

Various changes, arrangements and modifications may be applied to theabove-described illustrative embodiment. Like reference numerals may beused for like corresponding components and a detailed descriptionthereof with respect to the modifications may be omitted herein.

In the illustrative embodiment, such a control is executed that the inklanding/deposition sequence of primary colors from the nozzles 12 of thetransitional zones AR1 and AL2 of the head chips 11 c 1 and 11 c 2,which are arranged in staggered adjacency, is the same as the inklanding/deposition sequence of primary colors from the nozzles 12 ofother zones of the head chips 11 c 1 and 11 c 2 than the transitionalzones AR1 and AL2. This configuration results in the sub-zones a1-a3 ofeither or both of the transitional zones AR1 and AL2 of the head chips11 c 1 and 11 c 2 having unused nozzles which will not be used for theejection processing (e.g., the nozzles 12 represented by open circles inFIG. 5). No ink is ejected from nozzles to be unused, so that ink in theunused nozzles is dried and may become dense or concentrated. The headchip 11 typically includes common passages, each corresponding to arespective color of ink. The common passage is shared by the pluralityof nozzles 12. The denser or concentrated ink in the unused nozzles mayreach the nozzles to be used for ink ejection (e.g., the nozzles 12represented by solid circles in FIG. 5), via the common passages. Inthis case, the denser ink is to be ejected from the nozzles to be usedfor ink ejection, leading to deterioration of the quality of an image onthe recording sheet 100. Further, the denser ink whose viscosity hasincreased may clog the nozzles to be used for ink ejection. One solutionto this problem is to perform a maintenance operation to forciblydischarge ink from the all nozzles at a regular interval. However, suchmaintenance may lead to increase in waste ink because ink is forciblydischarged not only from the unused nozzles, but also from the nozzlesto be used, which may be greater in number than the unused nozzles. Therecording control IC 78 according to the modification is configured togenerate ejection data for controlling the inkjet head 4 such thatunused nozzles are reduced as much as possible. The modification isdescribed further below.

The memory 78 a stores therein a usage rate table, as depicted in FIG.10. The usage rate 100% in the usage rate table in FIG. 6 is modified to98% in the usage rate table in FIG. 10, and the usage rate 0% in theusage rate table in FIG. 6 is modified to 2% in the usage rate table inFIG. 10.

As can be seen from the usage rate table in FIG. 10, in the sub-zonesa1-a3, the head chips 11 c 1 and 11 c 2 may eject ink from the nozzlesof the sub-zone noncorresponding nozzle rows as well. For example, inthe sub-zones a1, the head chips 11 c 1 and 11 c 2 eject ink from thesub-zone corresponding nozzle rows of the nozzle rows 14C, as well asfrom the sub-zone noncorresponding nozzle rows of the nozzle rows 14Yand 14M. Ink ejection from the sub-zone noncorresponding nozzle rows ofthe head chips 11 c 1 and 11 c 2 is not intended to switch the use ofnozzle rows 14 between the head chips 11 c 1 and 11 c 2 (e.g., from thehead chip 11 c 1 to the head chip 11 c 2). Accordingly, such inkejection may have little effect in reducing print density unevennessthat may be caused by ink ejection from the nozzles 12 in either thetransitional zone AR1 of the head chip 11 c 1 or the transitional zoneAL2 in the head chip 11 c 2.

As described above, varying deposition sequence of primary color inksfrom the transitional zones AR1 and AL2 of the head chips 11 c 1 and 11c 2 and other zones of the head chips 11 c 1 and 11 c 2 than thetransitional zones AR1 and AL2, may cause differences in resulting huesof an image recorded on the recording sheet 100 (e.g., in the portion Aand the portion B). This may result in a deterioration of an imagequality. In this modification, in the sub-zones a1-a3 (e.g., the firstto third overlap sub-zones), usage rates of the nozzles 12 of thesub-zone noncorresponding nozzle rows sandwiched between the sub-zonecorresponding nozzle rows is specified as 10% or less, e.g. 2%, withrespect to the total number of nozzles 12 to be used in the sub-zonenoncorresponding nozzle rows of the head chips 11 c 1 and 11 c 2. Forexample, in the sub-zones a1 (e.g., the first overlap sub-zone), usagerates of the nozzle rows 14Y and 14M of the head chip 11 c 2, which aresandwiched between the nozzle rows 14C of the head chips 11 c 1 and 11 c2, is 2%, which is less than 10%. With this configuration, thedeposition sequences of the primary color inks from the nozzles 12 inthe transitional zones AR1 and AL2 (e.g., overlap head zone), may bealmost the same (e.g., at a greater rate) as the deposition sequences ofthe primary color inks from the nozzles 12 in other zones of the headchips 11 c 1 and 11 c 2 than the transitional zones AR1 and AL2. Thismay reduce hue difference in an image on the recording sheet 100 (e.g.,between the portion A and the portion B).

The recording control IC 78 according to the modification is configuredto generate ejection data for each of the head chips 11 c 1 and 11 c 2,to prevent particular nozzles 12 of the nozzle rows 14Y, 14M and 14C inthe respective sub-zones a1-a3 from being unused for a long period oftime. For example, as described above, the recording control IC 78 maychange mask patterns to be used in the ejection data generatingprocessing, for every predetermined number of lines of raster data.Alternatively, the recording control IC 78 may be configured togenerate, based on raster data, ejection data for each of the head chips11 c 1 and 11 c 2 such that the nozzles 12, which have longer unusedperiods, may be used preferentially. This may prevent or reduce ink inthe nozzles 12 in the transitional zones AR1 and AL2 of the head chips11 c 1 and 11 c 2 from becoming viscous. Accordingly, ink to be usedduring maintenance operation may be reduced.

Other modifications are described below.

The sub-zone a4 is provided overlapping with all of the three sub-zonesa1-a3 in the left-right direction (e.g., to fully cover the threesub-zones a1-a3 in the left-right direction). In another example, thesub-zone a4 may be provided overlapping with at least one of thesub-zones a1-a3 in the left-right direction, or partially overlappingwith the sub-zones a1-a3 in the left-right direction.

The third nozzle row, e.g., the nozzle row 14K, is configured to ejectblack ink in the illustrative embodiment. In another example, the thirdnozzle row may be configured to eject different color ink. Each of thefirst nozzle row and the second nozzle row, e.g., the nozzle rows 14Y,14M, and 14C, are configured to eject one of different color inks, e.g.,yellow, cyan, and magenta inks, in the illustrative embodiment. Inanother example, each of the first nozzle row and the second nozzle rowmay be configured to eject another color ink.

As described above, the head chip 11 includes the four nozzle rows 14C,14Y, 14M, and 14K, each configured to eject one of different color inks.However, the head chip 11 may not necessarily include four nozzle rows14, but may include at least three nozzle rows, each configured to oneof different color inks.

In the illustrative embodiment, the recording control IC 78 isconfigured to generate ejection data for controlling ejection times forthe nozzle rows 14C, 14Y, 14M, and 14K such that each of color inks ofyellow, cyan, and the magenta is deposited at a position different tothat of black ink in the conveyance direction. In another example, theimage processing IC 76 may be configured to generate intermediateejection data corresponding to a respective color, such that each ofcolor inks of yellow, cyan, and magenta may be deposited at a positiondifferent to that of black ink in the conveyance direction. The imageprocessing IC 76 may determine based on CMYK data whether an objectconstituting an image to be recorded on the recording sheet 100 includesonly monochrome text. Based on the determination that data of the objectincludes only monochrome text, the object may be formed in black ink. Inaddition, the image processing IC 76 may be configured to generateintermediate ejection data for a respective color such that a blackportion of an object other than monochrome text is formed by mixingprimary color inks into a tertiary color ink (so-called “compositeblack”).

In the illustrative embodiment, each of the sub-zones a1-a4 is dividedinto sections. However, each zone a1-a4 does not necessarily be dividedinto sections. In other words, the usage rates of the nozzles 12 in eachof the sub-zones a1-a4 does not necessarily change linearly but may beconstant.

As long as the arranging direction of the nozzles 12 of the nozzle rows14C, 14Y, 14M, and 14K crosses the conveyance direction, the arrangingdirection of the nozzles 12 may not be necessarily perpendicular ororthogonal to the conveyance direction.

In the above-described illustrative embodiment, the printer 1 is of aline type in which image recording is performed with the inkjet head 4fixed. In another example, a printer may be of a serial type in whichimage recording is performed with a print head scanning or moving in adirection crossing the conveyance direction of the recording sheet 100.In this case, the direction crossing the conveyance direction may be therelative moving direction.

What is claimed is:
 1. A fluid ejection apparatus, comprising: a firsthead chip extending from a first end in a first direction towards asecond end in the first direction, wherein the first head chipcomprises: a nozzle row A comprising nozzles A arranged along the firstdirection; a nozzle row B comprising nozzles B arranged along the firstdirection; and a nozzle row C comprising nozzles C arranged along thefirst direction; a second head chip extending from a third end in thefirst direction towards a fourth end in the first direction, wherein thesecond head chip comprises: a nozzle row D comprising a plurality ofnozzles D arranged along the first direction; a nozzle row E comprisingnozzles E arranged along the first direction; and a nozzle row Fcomprising nozzles F arranged along the first direction, a controllerconfigured to control the first head chip and the second head chip toeject fluid from the first head chip and the second head chip, whereinthe nozzle row B is positioned between the nozzle row A and the nozzlerow D in a second direction orthogonal to the first direction, whereinthe nozzle row D is positioned between the nozzle row B and the nozzlerow E in the second direction, wherein the nozzles A of the nozzle row Aare arranged into a nozzle group A1 and a nozzle group A2, wherein thenozzle group A1 comprises some of the nozzles A, wherein the nozzlegroup A2 comprises others of the nozzles A, wherein the nozzle group A1is positioned between the nozzle group A2 and the center of the firsthead chip in the first direction, wherein the nozzles B of the nozzlerow B are arranged into a nozzle group B1, wherein the nozzle group B1comprises some of the nozzles B, wherein the nozzle group A1 and thenozzle group B1 are aligned along the second direction, wherein thenozzles C of the nozzle row C are arranged into a nozzle group C,wherein the nozzle group C comprises some of the nozzles C, wherein thenozzle group A1 and a portion of the nozzle group C are aligned alongthe second direction, wherein the nozzles D of the nozzle row D arearranged into a nozzle group D2, wherein the nozzle group D2 of thenozzle row D comprises some of the nozzles D, wherein the nozzle groupA2 and the nozzle group D2 are aligned along the second direction,wherein the nozzles E of the nozzle row E are arranged into a nozzlegroup E1 and a nozzle group E2, wherein the nozzle group E1 comprisessome of the nozzles E, wherein the nozzle group E2 comprises others ofthe nozzles E, wherein the nozzle group A1 and the nozzle group E1 arealigned along the second direction, wherein the nozzle group A2 and thenozzle group E2 are aligned along the second direction, wherein thenozzles F of the nozzle row F are arranged into a nozzle group F,wherein the nozzle group F comprises some of the nozzles F, wherein thenozzle group A1 and a portion of the nozzle group F are aligned alongthe second direction, wherein the nozzle group C and the nozzle group Fare aligned along the second direction, wherein the controller isconfigured to control: the nozzle group A1 to eject fluid at an averageusage rate A1 that is an average of usage rates of the some of nozzles Acomprising the nozzle group A1; the nozzle group A2 to eject fluid at anaverage usage rate A2 that is an average of usage rates of the others ofnozzles A comprising the nozzle group A2; the nozzle group B1 to ejectfluid at an average usage rate B1 that is an average of usage rates ofthe some of nozzles B comprising the nozzle group B1; the nozzle group Cto eject fluid at an average usage rate C that is an average of usagerates of the some of nozzles C comprising the nozzle group C; the nozzlegroup D2 to eject fluid at an average usage rate D2 that is an averageof usage rates of the some of nozzles D comprising the nozzle group D2;the nozzle group E1 to eject fluid at an average usage rate E1 that isan average of usage rates of the some of nozzles E comprising the nozzlegroup E1; the nozzle group E2 to eject fluid at an average usage rate E2that is an average of usage rates of the others of nozzles E comprisingthe nozzle group E2; and the nozzle group F to eject fluid at an averageusage rate F that is an average of usage rates of the some of thenozzles F comprising the nozzle group F, wherein the average usage rateA2 is smaller than the average usage rate A1, wherein the average usagerate B1 is smaller than the average usage rate A1, wherein the averageusage rate C is smaller than the average usage rate A1, wherein theaverage usage rate D2 is smaller than the average usage rate E2, whereinthe average usage rate E1 is smaller than the average usage rate E2, andwherein the average usage rate F is smaller than the average usage rateE2.
 2. The fluid ejection apparatus according to claim 1, wherein thenozzle row C is positioned between the nozzle row B and the nozzle rowD, and wherein the nozzle row D and the nozzle row E are positionedbetween the nozzle row C and the nozzle row F.
 3. The fluid ejectionapparatus according to claim 1, wherein the nozzle group A2 and ananother portion of the nozzle group C are aligned along the seconddirection.
 4. The fluid ejection apparatus according to claim 1, whereinthe controller is configured to: control the nozzle row A and the nozzlerow D to form a first dot line corresponding to a particular line of anejection data, control the nozzle row B and the nozzle row E to form asecond dot line corresponding to the particular line of the ejectiondata, and control the nozzle row C and the nozzle row F to form a thirddot line corresponding to the particular line of the ejection date, andwherein a position of the third dot line on a recording medium in thesecond direction is different from each one of a position of the firstdot line on the recording medium in the second direction and a positionof the second dot line on the recording medium in the second direction.5. The fluid ejection apparatus according to claim 1, wherein the nozzlerow A and the nozzle row D are configured to eject a fluid of a firstprimary color, wherein the nozzle row B and the nozzle row E areconfigured to eject a fluid of a second primary color, and wherein thenozzle row C and the nozzle row F are configured to eject a fluid of ablack color.
 6. The fluid ejection apparatus according to claim 1,wherein the average usage rate A1 is 100%.
 7. The fluid ejectionapparatus according to claim 6, wherein the average usage rate E2 is100%.
 8. The fluid ejection apparatus according to claim 1, wherein thenozzles B of the nozzle row B are arranged into a nozzle group B2,wherein the nozzle group B2 comprises others of the nozzles B, whereinthe nozzle group B1 is positioned between the nozzle group B2 and thecenter of the first head chip along the first direction, wherein thenozzle group A2 and the nozzle group B2 are aligned along the seconddirection, wherein the nozzles D of the nozzle row D are arranged into anozzle group D1, wherein the nozzle group D1 comprises others of thenozzles D, wherein the nozzle group D2 is positioned between the nozzlegroup D1 and a center of the second head chip along the first direction,wherein the nozzle group A2 and the nozzle group D2 are aligned alongthe second direction, and wherein the controller is configured tocontrol: the nozzle group B2 to eject fluid at an average usage rate B2that is an average of usage rates of the others of nozzles B comprisingthe nozzle group B2, and the nozzle group D1 to eject fluid at anaverage usage rate D1 that is an average of usage rates of the others ofthe nozzles D comprising the nozzle group B2.
 9. The fluid ejectionapparatus according to claim 8, wherein the average usage rate B2 isless than or equal to 10%.
 10. The fluid ejection apparatus according toclaim 8, wherein the average usage rate D1 is less than or equal to 10%.11. The fluid ejection apparatus according to claim 1, wherein the usagerates of the others of nozzles A comprising the nozzle group A2 linearlydecrease between the others of the nozzles A in the first direction, andwherein the usage rates of the some of nozzles D comprising the nozzlegroup D2 linearly increase between the some of the nozzles D in thefirst direction.
 12. A fluid ejection apparatus, comprising: a firsthead chip extending from a first end in a first direction towards asecond end in the first direction, wherein the first head chipcomprises: a nozzle row A comprising nozzles A arranged along the firstdirection; a nozzle row B comprising nozzles B arranged along the firstdirection; and a nozzle row C comprising nozzles C arranged along thefirst direction; a second head chip extending from a third end in thefirst direction towards a fourth end in the first direction, wherein thesecond head chip comprises: a nozzle row D comprising a plurality ofnozzles D arranged along the first direction; a nozzle row E comprisingnozzles E arranged along the first direction; and a nozzle row Fcomprising nozzles F arranged along the first direction, a controllerconfigured to control the first head chip and the second head chip toeject fluid from the first head chip and the second head chip, whereinthe nozzle row B is positioned between the nozzle row A and the nozzlerow D in a second direction orthogonal to the first direction, whereinthe nozzle row D is positioned between the nozzle row B and the nozzlerow E in the second direction, wherein the nozzles A of the nozzle row Aare arranged into a nozzle group A1 and a nozzle group A2, wherein thenozzle group A1 comprises some of the nozzles A, wherein the nozzlegroup A2 comprises others of the nozzles A, wherein the nozzle group A1is positioned between the nozzle group A2 and the center of the firsthead chip in the first direction, wherein the nozzles B of the nozzlerow B are arranged into a nozzle group B1, wherein the nozzle group B1comprises some of the nozzles B, wherein the nozzle group A1 and thenozzle group B1 are aligned along the second direction, wherein thenozzles C of the nozzle row C are arranged into a nozzle group C,wherein the nozzle group C comprises some of the nozzles C, wherein thenozzle group A2 and a portion of the nozzle group C are aligned alongthe second direction, wherein the nozzles D of the nozzle row D arearranged into a nozzle group D2, wherein the nozzle group D2 of thenozzle row D comprises some of the nozzles D, wherein the nozzle groupA2 and the nozzle group D2 are aligned along the second direction,wherein the nozzles E of the nozzle row E are arranged into a nozzlegroup E1 and a nozzle group E2, wherein the nozzle group E1 comprisessome of the nozzles E, wherein the nozzle group E2 comprises others ofthe nozzles E, wherein the nozzle group A1 and the nozzle group E1 arealigned along the second direction, wherein the nozzle group A2 and thenozzle group E2 are aligned along the second direction, wherein thenozzles F of the nozzle row F are arranged into a nozzle group F,wherein the nozzle group F comprises some of the nozzles F, wherein thenozzle group A2 and a portion of the nozzle group F are aligned alongthe second direction, wherein the nozzle group C and the nozzle group Fare aligned along the second direction, wherein the controller isconfigured to control: the nozzle group A1 to eject fluid at an averageusage rate A1 that is an average of usage rates of the some of nozzles Acomprising the nozzle group A1; the nozzle group A2 to eject fluid at anaverage usage rate A2 that is an average of usage rates of the others ofnozzles A comprising the nozzle group A2; the nozzle group B1 to ejectfluid at an average usage rate B1 that is an average of usage rates ofthe some of nozzles B comprising the nozzle group B1; the nozzle group Cto eject fluid at an average usage rate C that is an average of usagerates of the some of nozzles C comprising the nozzle group C; the nozzlegroup D2 to eject fluid at an average usage rate D2 that is an averageof usage rates of the some of nozzles D comprising the nozzle group D2;the nozzle group E1 to eject fluid at an average usage rate E1 that isan average of usage rates of the some of nozzles E comprising the nozzlegroup E1; the nozzle group E2 to eject fluid at an average usage rate E2that is an average of usage rates of the others of nozzles E comprisingthe nozzle group E2; and the nozzle group F to eject fluid at an averageusage rate F that is an average of usage rates of the some of thenozzles F comprising the nozzle group F, wherein the average usage rateA2 is smaller than the average usage rate A1, wherein the average usagerate B1 is smaller than the average usage rate A1, wherein the averageusage rate C is smaller than the average usage rate A1, wherein theaverage usage rate D2 is smaller than the average usage rate E2, whereinthe average usage rate E1 is smaller than the average usage rate E2, andwherein the average usage rate F is smaller than the average usage rateE2.